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Category: algorithms Component type: function


template <class ForwardIterator, class OutputIterator>
OutputIterator rotate_copy(ForwardIterator first, ForwardIterator middle,
                           ForwardIterator last, OutputIterator result);


Rotate_copy copies elements from the range [first, last) to the range [result, result + (last - first)) such that *middle is copied to *result, *(middle + 1) is copied to *(result + 1), and so on. Formally, for every integer n such that 0 <= n < last - first, rotate_copy performs the assignment *(result + (n + (last - middle)) % (last - first)) = *(first + n). Rotate_copy is similar to copy followed by rotate, but is more efficient. The return value is result + (last - first).


Defined in the standard header algorithm, and in the nonstandard backward-compatibility header algo.h.

Requirements on types

  • ForwardIterator is a model of Forward Iterator.
  • OutputIterator is a model of Output Iterator.
  • ForwardIterator's value type is convertible to a type in OutputIterator's set of value types.


  • [first, middle) is a valid range.
  • [middle, last) is a valid range. [1]
  • There is enough space to hold all of the elements being copied. More formally, the requirement is that [result, result + (last - first)) is a valid range.
  • The ranges [first, last) and [result, result + (last - first)) do not overlap.


Linear. Rotate_copy performs exactly last - first assignments.


const char alpha[] = "abcdefghijklmnopqrstuvwxyz";
rotate_copy(alpha, alpha + 13, alpha + 26, ostream_iterator<char>(cout));
// The output is nopqrstuvwxyzabcdefghijklm


[1] It follows from these two requirements that [first, last) is a valid range.

See also

rotate, copy.
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